/*
 * Syncany, www.syncany.org
 * Copyright (C) 2011-2016 Philipp C. Heckel <philipp.heckel@gmail.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.syncany.util;

import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.util.Arrays;
import java.util.List;

/**
 * Utility class for common application string functions.
 *
 * @author Philipp C. Heckel (philipp.heckel@gmail.com)
 */
public class StringUtil {
	/**
	 * Transforms a string to a camel case representation, including the
	 * first character.
	 *
	 * <p>Examples:
	 * <ul>
	 *  <li><code>toCamelCase("hello world") -&gt; "HelloWorld"</code></li>
	 *  <li><code>toCamelCase("hello_world") -&gt; "HelloWorld"</code></li>
	 *  <li><code>toCamelCase("hello_World") -&gt; "HelloWorld"</code></li>
	 *  <li><code>toCamelCase("helloWorld") -&gt; "HelloWorld"</code></li>
	 *  <li><code>toCamelCase("HelloWorld") -&gt; "HelloWorld"</code></li>
	 * </ul>
	 */
	public static String toCamelCase(String str) {
		StringBuilder sb = new StringBuilder();

		for (String s : str.split("[-_ ]")) {
			if (s.length() > 0) {
				sb.append(Character.toUpperCase(s.charAt(0)));

				if (s.length() > 1) {
					sb.append(s.substring(1, s.length()));
				}
			}
		}

		return sb.toString();
	}

	/**
	 * Transforms a string to underscore-delimited representation.
	 *
	 * <p>Examples:
	 * <ul>
	 *  <li><code>toUnderScoreDelimited("HelloWorld") -&gt; "hello_world"</code></li>
	 *  <li><code>toUnderScoreDelimited("helloWorld") -&gt; "hello_world"</code></li>
	 * </ul>
	 */
	public static String toSnakeCase(String str) {
		StringBuilder sb = new StringBuilder();

		for (char c : str.toCharArray()) {
			if (Character.isLetter(c) || Character.isDigit(c)) {
				if (Character.isUpperCase(c)) {
					if (sb.length() > 0) {
						sb.append("_");
					}

					sb.append(Character.toLowerCase(c));
				} else {
					sb.append(c);
				}
			} else {
				sb.append("_");
			}
		}

		return sb.toString();
	}

	/**
	 * Converts a byte array to a lower case hex representation.
	 * If the given byte array is <code>null</code>, an empty string is returned.
	 */
	public static String toHex(byte[] bytes) {
		if (bytes == null) {
			return "";
		} else {
			final char[] hexArray = "0123456789ABCDEF".toCharArray();
			char[] hexChars = new char[bytes.length * 2];
			for (int j = 0; j < bytes.length; j++) {
				int v = bytes[j] & 0xFF;
				hexChars[j * 2] = hexArray[v >>> 4];
				hexChars[j * 2 + 1] = hexArray[v & 0x0F];
			}
			return String.valueOf(hexChars).toLowerCase();
		}
	}

	/**
	 * Creates byte array from a hex represented string.
	 */
	public static byte[] fromHex(String hexString) {
		if (hexString.length() % 2 == 1) {
			throw new IllegalArgumentException("hex string must be of even length");
		}

		char[] hex = hexString.toCharArray();
		byte[] raw = new byte[hex.length / 2];
		for (int src = 0, dst = 0; dst < raw.length; ++dst) {
			int hi = Character.digit(hex[src++], 16);
			int lo = Character.digit(hex[src++], 16);
			if ((hi < 0) || (lo < 0))
				throw new IllegalArgumentException();
			raw[dst] = (byte) (hi << 4 | lo);
		}
		return raw;
	}

	/**
	 * Creates a byte array from a given string, using the UTF-8
	 * encoding. This calls {@link String#getBytes(java.nio.charset.Charset)}
	 * internally with "UTF-8" as charset.
	 */
	public static byte[] toBytesUTF8(String s) {
		try {
			return s.getBytes("UTF-8");
		} catch (UnsupportedEncodingException e) {
			throw new RuntimeException("JVM does not support UTF-8 encoding.", e);
		}
	}

	/**
	 * Returns the count of the substring
	 */
	public static int substrCount(String haystack, String needle) {
		int lastIndex = 0;
		int count = 0;

		if (needle != null && haystack != null) {
			while (lastIndex != -1) {
				lastIndex = haystack.indexOf(needle, lastIndex);

				if (lastIndex != -1) {
					count++;
					lastIndex += needle.length();
				}
			}
		}

		return count;
	}

	public static String getStackTrace(Exception exception) {
		StringWriter stackTraceStringWriter = new StringWriter();
		exception.printStackTrace(new PrintWriter(stackTraceStringWriter));

		return stackTraceStringWriter.toString();
	}

	public static <T> String join(List<T> objects, String delimiter, StringJoinListener<T> listener) {
		StringBuilder objectsStr = new StringBuilder();

		for (int i = 0; i < objects.size(); i++) {
			if (listener != null) {
				objectsStr.append(listener.getString(objects.get(i)));
			} else {
				objectsStr.append(objects.get(i).toString());
			}

			if (i < objects.size() - 1) {
				objectsStr.append(delimiter);
			}
		}

		return objectsStr.toString();
	}

	public static <T> String join(List<T> objects, String delimiter) {
		return join(objects, delimiter, null);
	}

	public static <T> String join(T[] objects, String delimiter, StringJoinListener<T> listener) {
		return join(Arrays.asList(objects), delimiter, listener);
	}

	public static <T> String join(T[] objects, String delimiter) {
		return join(Arrays.asList(objects), delimiter, null);
	}

	public static interface StringJoinListener<T> {
		public String getString(T object);
	}
}
